The field of this invention relates to an improved form of a flexible electromagnetic pulse shielding conduit for electrical conductors, and more particularly an improved form of conduit over that which is described within U.S. Pat. No. 4,693,323, entitled "Flexible Electromagnetic Pulse Shielding Conduit", issued Sept. 15, 1987, by one of the present inventors.
In the past, it has been common to encase electrical conductors that extend from one location to another. The use of elongated electrical conductors is required for operating electrical equipment remote from the source of the electrical generating signal apparatus. A typical location where a substantial number of electrical conductors are utilized to operate remote equipment would be within an aircraft.
In the past, it has been common to principally shield the electrical conductors from moisture. When dealing with military equipment, and particularly when dealing with electrical conductors that operate critical electrical components, it also has been necessary to protect the conductors from exterior electrical disturbances. Common forms of exterior electrical disturbances are electromagnetic interference and radio frequency interference. It has been common in the past to construct shielding conduits to protect these electrical conductors from such types of interferences.
However, there is another type of interference from which electrical conductors are susceptible and that is termed "electromagnetic pulse". An electromagnetic pulse comes from sources such as a nuclear detonation. It has been found that even the detonation of a relatively small sized nuclear weapon, that is strategically placed within the atmosphere, can cause extensive amount of damage to electronic equipment over a wide geographical area. This damage manifests itself in two ways. One way is hardware damage, usually in the form of semiconductor burnout. The other way is electronic upset, usually in the form of a data transmission loss or loss of stored data.
An electrical conductor may be shielded against electromagnetic and radio frequency interference but not be shielded against electromagnetic pulse. This pulse, when picked up by the electrical conductor, is conducted into the electronic equipment. Any small aperture within a shielded electronic conductor conduit would provide for access of the pulse to the electrical conductor.
In the past, in order to prevent this superimposing of signals onto an electrical conductor, it has been common to encase the electrical conductor within a conduit formed by layers of braided metallic wires. In the constructing of such conduits, it has been common to use clamps and other similar types of mechanical fastening devices in order to secure the ends of these layers of braided wires to the electrical connector fitting (such as a backshell). However it has been found that, over a period of time during installation of these conduits, these mechanical connections become loosened resulting in the forming of small openings within the conduit. Any small opening within any conduit would make such conduit ineffective against protection of electromagnetic pulse. A single unprotected conduit within a bomber or fighter aircraft that is exposed, evenly minorly, to a nuclear explosion will most likely result in that aircraft becoming immediately inoperative.
At times, the length of such conduits may be quite small, no more than a few inches. A shielding conduit requires at each end some form of a fitting commonly referred to as a backshell. In the past, such a backshell in and of itself has been two to three inches in length. It is desirable to construct a backshell to be of the shortest possible length so that such shielding conduits can be constructed to be utilized to be short lengths as well as long lengths.
One type of method of connection between parts is called magnetic pulse forming. Magnetic pulse forming machines were first introduced in 1962. Since that time, magnetic pulse forming machines have been utilized to assemble a variety of manufactured articles which would be difficult and costly to assemble by conventional methods. Magnetic pulse forming is an assembly technique which utilizes a high intensity magnetic field to expand or contract metallic workpieces. Magnetic pulse forming is based on a rapidly changing magnetic field and the current induced in the electrically conductive workpiece. Magnetic pulse forming is capable of compressing or expanding metal members without direct physical contact and without lubricants or torque normally encountered in rolling and spinning operations.
A high flux density is necessary to perform such magnetic pulse forming. This flux density can be produced by discharging a capacitor through a coil for a period of a few microseconds. Thus, tremendous flux densities are produced for a short period of time. It is the magnetic force which moves the metal. In the case of a ring or band and this magnetic pulse being applied exteriorly thereof, this ring or band will in essence shrink and enclose a smaller area. This enclosing technique can be utilized to achieve an extremely strong, secure connection of different parts of a manufactured product.